In the context of war aid the British received Sherman tanks from the USA during the Second World War. The turrets were modified to allow them to take the heavy 17 pounder (about 90mm) anti-tank and artillery gun. The Sherman Firefly deployed only by the British was a hybrid of the American's many manufacturing series and had the most powerful gun of all manufacturing runs. With armour-piercing ammunition the fire of the heavy German tanks could now be countered earlier and the losses significantly reduced. This 32.7-tonne tank was introduced in 1943 and immediately incorporated into the armoured units. The tank was very successful although it could not be produced in large numbers. The 5-man crew had an ammunition stock of 77 rounds and the 425 horsepower Chrysler engine could accelerate the Firefly to up to 40 kph.